Insulin capture by a G-quadruplex DNA oligonucleotide containing a two-repeat sequence of the insulin-linked polymorphic region (ILPR) of the human insulin gene promoter region is reported. The immobilized oligonucleotide was demonstrated to capture human insulin from standard solutions and from nuclear extracts of pancreatic cells with high selectivity, using affinity MALDI-mass spectrometry and affinity capillary chromatography. Insulin was preferentially captured by the tworepeat ILPR oligonucleotide over another G-quadruplex forming oligonucleotide, the thrombin binding aptamer, as well as over a single repeat of the ILPR sequence that is not capable of forming the G-quadruplex architecture. Binding was shown to involve the beta chain of insulin, most likely through association with the two parallel loops of the G-quadruplex structure. The discovery raises the possibility that insulin may bind to G-quadruplex DNA formed in the ILPR in vivo and thereby play a role in modulation of insulin gene expression, and provides a basis for design of insulin analogs to probe this hypothesis. The availability of a DNA ligand to human insulin has analytical importance as well, offering an alternative to antibodies for in vitro or in vivo detection and sensing of insulin as well as its isolation and purification from biological samples.

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A logistic regression model was developed to predict ethnic group from mitochondrial DNA (mtDNA) types determined by hybridization with sequence-specific oligonucleotide (SSO) probes of the two hypervariable segments of the mtDNA control region. The model was developed with, and tested against, a previously reported data set of 525 individuals from five ethnic groups (African-American, Southeast Asian, Caucasian, Japanese, and Mexican) involving 23 probes at nine regions within the two hypervariable segments [1]. The model correctly predicted the ethnic group of 65.3% of the overall sample; however, the success rate varied substantially among ethnic groups, with the most success obtained with Caucasians (81% correctly classified). A discriminant analysis yielded similar results. An example is given of using the model to predict the ethnic group of an SSO-type from a forensic case. Such models provide alternatives to traditional skeletal-based methods of predicting ethnicity, especially in cases where skeletal material is absent or incomplete.

In July 2021, foliar symptoms characterized by small, circular, light brown to tan lesions (0.5 to 3 mm diameter) with reddish-brown margins were observed on field corn (Zea mays L.) in two commercial fields in Hinds and Marion counties, Mississippi. Disease severity ranged from 2 to 15% on observed leaves. Symptomatic leaves were sealed in plastic bags, stored on ice, and transferred to the laboratory. Lesions were cut into small sections (≈4 mm2) and surface-sterilized with 70% ethanol for 30 s then rinsed with sterile water. Sterilized sections were transferred to potato dextrose agar (PDA) amended with chloramphenicol (75 mg/liter) and streptomycin sulfate (125 mg/liter) and incubated at 25°C in the dark for 7 days. Gray to brown-black colonies with orange margins and melanized, curved conidia with three transverse septa were observed microscopically (Fig. 1; ×400). Conidia measurements ranged from 15 to 25 μm in length and 7.5 to 12.5 μm in width (x̄= 20 × 9.8 μm; n= 44). Colony and conidia morphology were consistent with previous descriptions of Curvularia lunata (Wakker) Boedijn (Mabadeje 1969; Ellis 1971). Pure cultures were obtained, and DNA was extracted from 9-day old cultures. Two isolates (TW003-21; TW008-21) were selected for sequencing of the internal transcribed spacer (ITS) region using ITS4 and ITS5 primers. The 530-bp consensus sequences were deposited in GenBank under the accession No. OK095277 and OK095278. BLASTn queries of NCBI GenBank showed that the sequences shared 100% identity with C. lunata isolate DMCC2087 from Louisiana (MG971304) and isolate CX-3 from China (KR633084). A pathogenicity test was performed on V4/V5 stage corn plants (Progeny 9114VT2P) grown in 10.2 cm pots in the greenhouse. Plants were transferred to a growth chamber one-week prior to inoculation. The two isolates were grown on amended PDA for 14 days at 25°C and an inoculum suspension was prepared for each isolate by rinsing culture plates with 2 ml of autoclaved reverse osmosis (RO) water amended with Tween 20 (0.01%) and re-suspended into 40 ml of RO water containing Tween 20. The final concentration was adjusted to 2.6×105 conidia/ml (TW003-21) and 2×105 conidia/ml (TW008-21). Ten corn plants were sprayed with 10 ml of inoculum suspension for each isolate using a Preval sprayer with a CO2 canister, and 10 plants were sprayed with water containing Tween 20 only. Plants were incubated in a growth chamber at ≈79% relative humidity and 25°C. Foliar symptoms including small, circular, and tan lesions, similar to those observed in the field, developed 3 days after inoculation. No symptoms were observed on control plants. Following incubation, symptomatic leaves were collected and C. lunata was re-isolated as described above. Colony, spore morphology and DNA sequences from inoculated plants were consistent with the original isolates as described above. The disease has been recently reported in Louisiana (Garcia-Aroca et al. 2018), Kentucky (Anderson et al. 2019), and Delaware (Henrickson et al. 2021). Although Curvularia leaf spot has been observed sporadically in MS corn fields since 2009 (Allen, personal communication), to our knowledge, this is the first official report of the disease in MS. While this disease has been more frequently encountered in MS, the economic impact associated with C. lunata is currently unknown. References Anderson, N. R., et al. 2019. Plant Dis. 103:2692. Chang, J., et al. 2020. J. Integr. Agr. 19:551-560. Ellis, M. B. 1971. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, England, p. 452-458. Garcia-Aroca T., et al. 2018. Plant Health Prog. 19:140. Henrickson M., et al. 2021. Plant Dis. First Look. Mabadeje, S. A. 1969. Trans. Br. Mycol. Soc. 52:267-271. † Indicates the corresponding author. E-mail: twilkerson@drec.msstate.edu